> But now for 4cores/2CPUs per Opteron node to force the using of
> only 2 cores (from 4), by 1 for each chip, we'll need to have
> cpu affinity support in Linux.
Mikhail,
you can use "taskset" for that purpose.
For example, (perhaps not in the most elegant form)
mpiexec -n 1 taskset -c 0 $code : -n 1 taskset -c 2 $code
But I doubt you want to let the idle cores to do something else
in the mean time. However small you will generally see an increase
in performance if you use all the cores.
Best,
Igor
I. Kozin (i.kozin at dl.ac.uk)
CCLRC Daresbury Laboratory
tel: 01925 603308
http://www.cse.clrc.ac.uk/disco
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